Measurement of gain and evaluation of photon avalanche efficiency in 10Tm:KY(WO/sub 4/)/sub 2/ crystal pumped by free-running Nd:YAG laser

摘要

Potassium yttrium tungstate crystals (KYW) with 10% thulium content were grown by the modified Czochralski technique from solution in K/sub 2/W/sub 2/O/sub 7/ melt. For gain measurements the facets of a 10%Tm:KYW plate were AR coated at both pump and probe beam wavelengths. The output of free-running Nd:YAG laser was focused by lens at the aperture (309 /spl mu/m in diameter) which was transmitting 85% of the pump, and the sample was maintained just behind the aperture. The photon avalanche efficiency is proven to be rather high (/spl eta/0.7) up to the population of /sup 3/F/sub 4 /manifold N/sub 2//spl sim/2N which allows lasing at /spl sim/1.9 /spl mu/m. Due to a low threshold of photon avalanche, Tm:KYW and Tm:Yb:KYW crystals can be excited heavily with emission of high power laser diodes at /spl sim/1.06 /spl mu/m.